To talk about actions or situations that take place at the same time, we can use as, when or while.
All three words can be used to introduce longer background actions that are/were going on when something else happens/happened.
- The telephone rang when I was having a bath.
- While they were watching TV, thieves broke into the house.
- As I was reading the paper, I heard a loud noise.
As-clauses usually go at the beginning. When and while-clauses can go at the beginning or end of sentences.
We usually use a continuous tense for the longer background action. But note that as and while can also be used with simple tenses.
Simultaneous long actions
To talk about longer actions that go on at the same time we use while. Note that both continuous and simple tenses can be used with while.
- While Susie cleaned the floor, Alice washed the clothes.
- While Jane was reading, I was working in the garden.
As can be used with simple tenses to talk about two situations which change together.
- As you get older you get wiser.
Simultaneous short actions
To talk about two short actions that happen/happened at the same time, we use as or just as.
- As I opened my eyes I saw a strange sight.